A ministerial press conference in the middle of a trade fair from which politics are vetoed? Like so much that he has said down the years, Tony Benn's comment describing the Labour party conference in G2 yesterday contains just enough truth to be plausible to the unwary, while simultaneously oversimplifying a process for which he himself bears no small historic responsibility.

Yet Benn is on to something all the same. Having spent five of the past six weeks at party political conventions and conferences on either side of the Atlantic, I believe it is obvious democratic politics deserves better than this annual ritual and that something needs to be done about British party conferences.

Let us, though, recognise a few realities that Benn ignores. There never was a golden age of party conferences. They evolved because they could not survive as they were. Labour conference was never the people's parliament that rose-tinted memory suggests. A lot of the time they were stitch-up sessions in which male union chiefs traded millions of unconsulted votes to obtain ends which were as often conservative as progressive, and which routinely ignored the interests and views of Labour members, voters and governments alike.

Tory conferences of earlier times were unreformed anachronisms too, albeit of a different kind. Too often nasty, deferential and short, they never pretended to be democratic or deliberative, much less representative. They were rallies of the faithful, the fanatical and their wives. MPs of a delicate disposition gave these conferences a wide berth, while ministers arrived, spoke and departed as quickly as possible. Not even the leader always attended.

Old-style Liberal assemblies, by contrast, the last of which took place 20 years ago in a snowy January in an icy and forbidding Blackpool hotel, improbably chaired by the brother of the composer of Salad Days, had all the opposing faults: excessive length, openness and encyclopaedic attention to detail, fatally combined with irrelevance.

Nor is it true that today's conferences are as completely gelded as fashionable commentary sometimes pretends. Labour conferences still vote, though without the existential drama of yesteryear, and Labour, for all its many controlling sins, remains the one party at which floor delegates can still catch the eye of the chair and get to make an unvetted speech from the platform. You have to be called by name at the Lib Dem conference to do that these days. The Tories, meanwhile, have gone still further down the controlling road. Not only do they never vote; they don't even have a rostrum any more. William Hague and Edwina Currie could not make their names there today.

Yet politics at conferences continues. Benn is silly to pretend that a form of politics he dislikes is somehow not politics at all. You couldn't sit through the Lib Dem debate on tax and spend at Bournemouth without understanding what was at stake. Nor listen to Gordon Brown's speech in Manchester - or David Miliband's - without recognising these as conference moments of a kind that Nye Bevan or Hugh Gaitskell would have understood. Even David Cameron's three speeches in Birmingham told a tale of anxiety and indecision for those who were prepared to see it.

The fringes remain genuinely important too. Admittedly, there has not been a fringe meeting these 20 years to compare with the Tribune rally in Brighton in 1981, my first Labour conference as a reporter, when Margaret Beckett denounced Neil Kinnock as a Judas for not voting for Benn as deputy leader. And you rarely hear speeches at a Tory fringe like the encoded dissidence that Michael Heseltine or Geoffrey Howe used to bring so compellingly to the seaside in the Thatcher years.

Yet if you wanted to understand the seriousness with which the Tory party of 2008 is now preparing for power, then the on-message fringe meetings at this week's Birmingham conference told you a lot. The Labour fringe at Manchester, just as tellingly, offered a fringe conference of the Labour heart running in parallel to the conference of the Labour head in the official hall.

Yet party conferences, even in their modern, disciplined, best-behaviour mode, still matter. In 2005, the Tory party conference killed David Davis's leadership hopes dead, and transformed Cameron into the likely winner. That was also the year when a shout from Walter Wolfgang in the gallery during a speech by Jack Straw became the lightning rod for New Labour's illiberalism. Last year, the contrast between Brown's boasting and Cameron's straightforwardness turned the party battle on its head in the Tories' favour.

Party conferences have changed for three main reasons. The first is that they reflect changes in society itself. Greater prosperity has fostered greater ideological convergence. The antagonisms of even a generation ago, let alone of a century ago, have been blurred and blunted. Those who want to revive them have been marginalised not by a conspiracy but by progress. The conferences have become more centrist and more convergent, just like the voters.

The second change was television. Though the broadcasters no longer pay as much attention to the annual gatherings - not least because in the 24/7 media world the politicians are all permanently available anyway - they have relentlessly dictated changes in political style and appearance to fit the TV era. The pressure to avoid open dissent on TV cannot be laughed off as mere control-freakery.

The third change is money. Political parties cannot pay for conferences without the rental income they get from selling space at the conference site to lobbyists and companies, and without sponsorship that only large donors can provide. Judging by the Tory conference this week, I bet the party made a profit.

That is why, if you want to change conferences for the better - not to take them back to some non-existent and irrecoverable golden era but to make them more open and honest about the discussion of political and policy options, and less dominated by money and lobbyists - then money is the only weapon available. State funding of political parties should be your goal.

If you want parties under an obligation to conduct their conferences with more open debates and under other democratic rules, then place conditions on the state funding that they crave. Anything else is crying for the moon.martin.kettle@guardian.co.uk